The invention relates generally to security systems, and more particularly to biometric identification systems.
The human iris is commonly used as a biometric identifier in security systems due to high recognition rates, negligible false recognition rates, and contactless collection. Iris imaging is typically done using illumination with a spectrum centered around 800 nm. The spectrum of light used is restricted by the sensitivity of the detector. Typically, Silicon-based detectors are used, which have reduced sensitivity above 900 nm and negligible sensitivity above 1000 nm. A disadvantage to using illumination at these wavelengths is that the amount of illumination must be limited to protect the human eye from damage. Accordingly, since the level of illumination is diminished, a subject must be at a short distance, i.e., about one foot, from an image capturing device to capture an iris image of desirable quality for identification without the use of particularly sensitive cameras. Further, some eye colors do not lend themselves to easy image capture. For example, while blue eyes are generally easier to capture iris images of, brown eyes are not.
It is desirable to image the iris from longer distances such as, for example, about three meters. Further, in current iris imaging systems, the subject has to pause and hold his/her face close to the image capturing device, and obtaining a good image often requires user training and feedback from the imaging systems. Rapid iris image collection with minimal cooperation or delay as the subject walks past a biometric identification checkpoint will enable more applications of iris imaging systems. In addition, imaging the iris from longer distances requires usage of expensive image capturing devices and poses technical challenges.
Therefore, an improved iris imaging system is desirable to address one or more of the aforementioned issues.